/Engine/Source/Runtime/WebBrowser/Public/IWebBrowserSingleton.h
Delete old/unused web cache paths. Some Web implementations (i.e CEF) use version specific cache folders, this call lets you schedule a deletion of any now unused folders. Calling this may resulting in async disk I/O.
void ClearOldCacheFolders ( const [FString](API\Runtime\Core\Containers\FString) & CachePathRoot, const [FString](API\Runtime\Core\Containers\FString) & CachePrefix )